There's probably an extremely banal way: just set your system clock to a date
preceding the certificate expiration :)

It's likely to work.

Remember to disable any automatic time synchronization first.

Unfortunately though this will make the certificates of a lot of other sites
"unborn", so some external stuff will probably not be fetched.

There's also a slight chance that this gives you some problem on the system,
if there's some application that depends strongly on a not-too-wrong date. The
same when you reset back the date to the correct one (some old scheduled tasks
might get executed again?).


An alternative, it looks like httrack uses OpenSSL, maybe it's possible to
change its configuration with some environment value (OPENSSL_CONF pointing to
a .cnf file?) ; I don't know, on what I'm using now I just found out that
httrack *always* accepts expired certs! Bah...
I'm not sure what you'd put in that cnf file anyway, maybe
[ x509 ]
no_check_time
, but quite likely it's not even possible (I'm no OpenSSL expert).


Last chance, find a proxy software that allows accepting invalid certificates
and run httrack through it. I imagine there are, but I'm not familiar with
any.


Or really last chance, I do it for you, since it looks like expired
certificates are no skin off my httrack's nose... :/